Paleoanthropological Research in the Kibish Formation, Ethiopia

点击翻译按钮获取中文摘要

The origin of anatomically modern humans is one of the most exciting and hotly debated topics in human evolution today. The results of numerous genetic studies indicate that modern humans arose in Africa sometime during the last 200,000 years and subsequently migrated to other parts of the world. While the paleontological record of human evolution in Africa during this time period seems to support this scenario, the evidence is beset by many uncertainties as many of the critical fossils are known from fragmentary remains and have proved difficult to date precisely. For example, the purported remains of early modern early modern humans from South Africa are very fragmentary, while the more complete remains from Tanzania and Kenya have proved very difficult to date confidently. For over three decades, the paleontological remains from the Kibish Formation in southwestern Ethiopia have provided critical evidence of anatomically modern humans in subsaharan Africa more than 100,000 years ago. However, the Kibish fossils have also been the subject of debate because of uncertainties regarding their actual age, and the indications that two very different types of fossil hominid are preserved within these deposits- one relatively archaic and another more modern. Resolution of the actual ages of these fossils will contribute substantially to our understanding of the timing of human evolution in Africa and the origin of lineage leading uniquely to modern humans. An initial survey expedition in the Kibish Formation was undertaken in 1999 to explore the possibilities and promise of continued fieldwork there. Results of the 1999 season include a preliminary tephrostratigraphic framework for the Kibish Formation in the area where the 1967 fossils were discovered and 40Ar/39Ar dates for tuffaceous deposits bracketing the 1967 cranial remains. These indicate that the Omo 1 and Omo 2 cranial remains are unlikely to have come from the same stratigraphic horizon and that the hominids are between 100,000 and 200,000 years old with other deposits probably extending back to 300,000 years. We also doubled the mammalian fauna known from the Kibish formation and found stone tools throughout the Kibish Formation, including instances of tools associated with faunal remains bearing cutmarks. The overall goals of the research are: 1) To strengthen and refine the numerical control on the age of the Kibish Formation through additional fieldwork and analyses; 2) to refine the stratigraphic and temporal framework for previously collected fossils and establish a broad regional framework for future research; 3) to relate the sedimentology of the Kibish Formation to regional climatic changes; and 4) to locate additional paleontological and archeological localities within this chronometric, stratigraphic and sedimentological framework. Accomplishment of these goals will greatly advance our current understanding of human evolution and modern human origins in Africa during the past 300,000 years, the place and time in which or species first evolved.